Electron discharge tube



June 2, 1936. COHN 2,042,506

ELECTRON DISCHARGE TUBE Filed Feb. 25, 1954 INVENTOR ATTORNEY PatentedJune 2, 1936 UNITED STATES ELECTRON DISCHARGE TUBE Henny Gohn, Berlin,Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphiem. b. H., Berlin, Germany, a corporation of Germany Application February23, 1934, Serial No. 712,553 In Germany February 22, 1933 10 Claims.

(Granted under the provisions of sec. 14, act of March 2, 1927; 357 0.G. 5)

The present invention is concerned with an electrode system in which,apart from a main discharge gap, there is provided an auxiliarydischarge gap independent of the former.

Preference is being given nowadays in the art of radio receivers tocircuit schemes in which such volume fluctuations as are occasioned byatmospheric phenomena are compensated. For this purpose the aggregategain of the receiver is usually so adjusted by the variation of the gridbiasing voltage of a radio frequency amplifier tube as a function of theprevailing incoming field intensity that the audio frequency outputpotential remains stable and unvaried. The regulator voltage consists ofa rectified carrier wave of the particular transmitter station that isbeing received, derived from the plate circuit of a rectifier, generallythe demodulator. In order that separate compensator batteries may bedispensable, recourse is had for rectification to twoelectrode tubes ordiodes which operate without any additional direct voltage or at mostwith only low voltage. Inasmuch as the discharge current of such arectifier gap is low it is feasible to combine the second electrodesystem constructionally inside a common glass bulb with the tubeelectrodes of the same circuit scheme or another consecutive tube.

In the embodiments of combination or compound tubes of the said sortheretofore used the cathode is extended, so that it protrudes-beyond theelectrode system, and over this free or projecting end are shifted oneor two anodes, depending upon whether half-wave or full-waverectification is desired. This type of construction involves thedrawback that the cathode must be extended, requires more heatingenergy, and that supplementary shielding means which tend to make theconstruction essentially more expensive, are absolutely necessary inorder that the rectifier system may be uncoupled electrically inreference to the main discharge path. Another point that must be kept inmind is that owing to the greater length of the electrode structure thetube will evidence a greater tendency to develop microphonic noises.

Now, the present invention discloses an electrode system whichrepresents a simple solution of this problem. The invention ispredicated upon the fact that the lateral end face of an indirectlyheated cathode is made emissive and utilized as the source of anauxiliary discharge. The indirectly heated cathode consists of a ceramicbody in the interior of which the heater proper is accommodated. Theouter surface of cally in Figs..l to 6 of the accompanying drawing.

Referring to Fig. 1, K denotes an indirectly heated cathode ofcylindrical form, G is the grid electrode, and A the anode of a triodesystem. The end face K of the cathode is also rendered emissive, andface to face therewith there is mounted an auxiliary anode H. In orderthat the capacity of the auxiliary electrode in reference to theamplifier system may be minimized,

' the auxiliary electrode shown in Fig. 2 may consist of a wire H whichis positioned coaxially with respect to the cathode. In this case,additional shielding will not be necessary.

But if some shielding is inevitable, this can be provided by the simpleconstruction disclosed in Fig. 3, wherein R. denotes the tiny insulationtube containing the heater, upon which is shifted in the usual way aslender metal tube or. sleeve M which is coated with anelectron-emissivelayer 0. At the end facing the auxiliary anode H themetal tube has a flange F on which is fastened a metallic shield S, forinstance, by welding. In order to perfect the shielding, the saidshield. S may also be provided with an annular extension S. Directlyover the end of the small insulation tube, the shield 'S is activated bycoating it with. a small quantity of emissive substance 0'.

Fig. 4 discloses a construction whereinthe shield S is united in asimple way with an insulating disc which serves to support and space theseveral electrodes. In this modification K, G, and

A are respectively the cathode, grid and anode of the electrode system,said elements being sup-'- ported and suitably spaced by the 'aid of aninsulation disc J of ceramic or other suitable material. The upper faceof disc J adjacent the auxiliary anodeH" is provided with'a metalliccoat or film O which is united with the cathode coat, and which mayconsist of a metal foil, of a layer made by a spray process, or thelike. Of course, care must be taken so that the grid and anode supportwires T will not contact with the metal shield S in order to avoidshort-circuiting between the electrodes.

Since the end of the cathode is naturally subing of the cathode end.Fig. 5 discloses a suitable method by which this may be accomplished,the turns of heater wire D which are disposed within the insulation tubeB being wound somewhat more closely at one end than in the middle of thecathode. s

V The idea underlying the present invention, of utilizing a cathodeportion which is unused for the major discharge path by convenientlymounting means for an auxiliary discharge path, ..will be found usefulin different ways in connection with other forms of cathode. Forinstance, flat cathodes are known in the art whose ceramic body is ofrectangular form. The suggestion has been made with a view to insuring ahomogeneous field shape to activate only the broad sides of such acathode body, while leaving the edges and narrow sides or faces thereofnon-emissive. In cathodes of this type one or both narrow sides may beutilized to act as cathode areas for an auxiliary discharge gap or gaps.Fig. 6 shows a cross-section through such an electrode system, where Crepresents the cathode or the carrier member for the cathode, G the gridelectrode consisting of a metal gauze or fabric which is laid about twosupport or stay wires T and is fastened thereto. The anodes A are shownarranged in parallel planes although other anode forms may be used. Thetwo broad sides of the cathode are provided with electron-emissive coatsC,'while the narrow sides are coated with active substance as indicatedat C" for supplying the electrons for the auxiliary discharge gaps. Theauxiliary anodes P may, for instance, be made from wires or narrowstrips of sheet material, and these may be connected in parallel forhalf-wave rectification or else may be connected to operate as push-pullor full-wave rectifiers.

What I claim is:

1. An electron discharge tube comprising a unitary cathode structureprovided with arcuate and planar electron emitting surfaces and anelectron collecting electrode cooperating with each of said. emittingsurfaces to form therewith a plurality of independent discharge paths.

2. An electron discharge tube comprising a thermionic. cathode axiallydisposed therein and having a plurality of surfaces, one of which emitselectrons radially and another of which emits electrons axially, and aplurality of electrodes cooperating with said cathode surfaces to formindependent discharge paths.

3. An electron discharge tube comprising a cathode axially disposedtherein and having a plurality of surfaces, one of which emits electronsradially and another of which emits electrons axially, a plurality ofelectrodes cooperating with said cathode surfaces to form independentdischarge paths, and an electrostatic shield interposed between saiddischarge paths.

4. An electron discharge tube comprising a cathode axially disposedtherein and having a plurality of surfaces, one of which emits electronsradially and another of which emits electrons axially, a plurality ofelectrodes cooperating with said cathode surfaces to form independentdischarge paths, and an electrostatic shield, conductively connected tothe cathode, interposed between said discharge paths.

5. An electron discharge tube comprising an electron emitting electrodehaving arcuate and planar surfaces, an amplifier anode cooperating withsaid arcuate emitting surface and forming therewith the principaldischarge path, and a rectifier anode cooperating with the planaremitting surface and forming therewith an auxiliary discharge path whichis substantially at right angles to the principal discharge path.

6. An electron discharge tube comprising an electron emitting electrodehaving arcuate and planar surfaces, an amplifier anode cooperating withsaid arcuate emitting surface and forming therewith the principaldischarge path, a rectifier anode cooperating with the planar emittingsurface and forming therewith an auxiliary discharge path which issubstantially at right angles to the principal discharge path, and anelectrostatic shield, conductively connected to the emitting electrodeinterposed between said discharge paths.

7. An electron discharge tube comprising a thermionic cathode having asubstantially cylin- I;

drical electron emitting surface and a planar emitting surface, and anelectron collecting electrode independently cooperating with each ofsaid emitting surfaces. 7

8. An electron discharge tube comprising an electron emitting memberhaving an axially disposed metallic sleeve coated with an electronemissive substance, a shield member connected to said metallic sleeveand projecting in a plane perpendicularly to the sleeve axis, aplurality of electrodes concentrically arranged about said metallicsleeve and disposed to one side of said shield, and an auxiliaryelectrode mounted on the other side of said shield and close to themetallic sleeve. 9. An electron discharge tube comprising a metallicsleeve coated on its outer surface with an electron emissive substance,a metal disc member laterally disposed over the edge of the metallicsleeve and connected thereto, the metal disc being provided on itsexternal side with a coating of electron emissive substance, anelectrode mounted on that side of the metal disc having the electronemissive coating, and a plurality of electrodes mounted on the otherside of the metal disc and surrounding the coated metallic sleeve.

10. An electron discharge tube comprising a cylindrical cathode, gridand anode electrodes surrounding the cathode, an insulating disc mountedat one end of said electrodes, a shield supported on said insulatingdisc and having that portion thereof which is in alignment with thecathode coated with an electron emissive substance, and an auxiliaryelectrode positioned to cooperate with said coated portion of theshield.

HENNY COHN.

